1. Field of the Invention
The present invention relates generally to coating compositions suitable for thermosetting applications, which compositions are based upon (A) compounds containing activated unsaturated groups and (B) compounds containing activated CH groups.
2. Description of Background Art
These compositions are, in general, known from a number of references including U.S. Pat. No. 2,759,913, DE-PS-835809, U.S. Pat. No. 4,871,822 (EP-A-0160824), U.S. Pat. No. 4,602,061, U.S. Pat. No. 4,408,018 and U.S. Pat. No. 4,217,396 (GB-A-2048913), all of which are incorporated by reference herein for all purposes.
For example, U.S. Pat. No. 2,759,913 and U.S. Pat. No. 4,871,822 generally disclose a composition of the above type which may be cured at ambient and elevated temperatures. More specifically, these references generally describe, as component (A), compounds containing at least two activated ethylenic double bonds and, as component (B), a wide variety of compounds including those containing at least two activated methylene and/or monosubstituted methylene groups.
U.S. Pat. No. 4,602,061 discloses a similar composition except that, as component (B), are specifically mentioned malonic group-containing oligomeric and polymeric esters.
U.S. Pat. No. 4,408,018 and U.S. Pat. No. 4,217,396 again disclose similar compositions except that, as component (B), are specifically mentioned acetoacetate groups-containing compounds.
It is also known from these references, and in general, that components (A) and (B) will react in the presence of a strong basic catalyst via a Michael addition. Because such catalyst is strongly basic, however, it has a tendency to become deactivated in the presence of certain acidic additives (e.g., certain pigments) or when the composition is applied to substrates having an acidic nature.
This effect can be overcome by increasing the amount of catalyst; however, the result is often an unacceptably short potlife. This disadvantage is exacerbated by the use of elevated temperatures.